There are known and used various type methods for inspecting liquid by employing a photoelectrical element besides the macroscopic inspecting methods for checking and determining the presence of extraneous or alien solid substances which may exist in admixture, for example, in medical liquids, liquid food and drink, cosmetics, liquid chemicals and reagents in the liquid state contained in a transparent container, for example, an ampoule, a vial, bottles or other kinds of containers.
This invention is concerned with the improvement of the type of method wherein the intensity of light passed through the liquid to be inspected is measured, and more particularly to a method which a container such as ampoule is illuminated and then a photoelectric element measures the extent of interception of light beams due to extraneous substances which may exist in the liquid in the container. The photoelectric element receives the light beams which penetrates through the liquid in the container without interception when no extraneous substance exists in the liquid. However, when extraneous substances do exist in the liquid part of the light beams are intercepted by the extraneous substance, and there is a decrease in the amount of the light reaching the photoelectric element. Thus, the amount of the extraneous substance in the liquid can be determined by measuring of the decrease in light.
Generally speaking, the higher the rotating speed of a rotating scan head on an optical fiber line-circle converter used in the above-mentioned system in which the light beams are passed through the liquid is measured, the more the performance of the system for detecting the extraneous solid substance is enhanced, because, due to the random motion of the extraneous substance, the higher the speed of operation or rotation, the higher the probability of detection. (However, an increased rotating speed in excess of about 5000 r.p.m. caused difficulty in mechanical structure.)